유현우 (한국표준과학연구원)

김병주 (한국표준과학연구원)

최기환 (한국표준과학연구원)

유현우 (한국표준과학연구원)

김병주 (한국표준과학연구원)

최기환 (한국표준과학연구원)

This study presents the development of a method for the accurate determination of vitamin B12 (cobalamin) in infant formula using isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS). [13C7]-cyanocobalamin isotope-labeled analogue was used as an internal standard. The concentration of the cyanocobalamin (CN-Cbl) standard solution was determined through qNMR, and validated using CE-UV for precise quantification. The response factor of LC-MS/MS obtained from qNMR-measured standard concentrations showed improved precision, with an RSD of 4.56% compared to the gravimetric method, with an RSD of 13.34%. The concentration of CN-Cbl standard solution measured by qNMR was subsequently applied to the analysis of vitamin B₁₂ in infant formula. The cobalamin contained in infant formula was converted to cyanocobalamin by the cyanidation process. Because residual hydroxocobalamin (OH-Cbl) was still detected in the chromatogram, the total cobalamin concentration, including the concentration of OH-Cbl, was measured as the corrected measurement results. The uncertainty of the corrected measurement results was calculated by incorporating the component of OH‑Cbl concentration (1.98 %–2.53 %). The developed method showed that an accuracy of 102% and inter- and intraday variation of less than 1%. The method was applied to commercially available infant formula, with cobalamin concentrations ranging from 33.33 µg/kg to 44.22 µg/kg.

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